While those who work in freshwater conservation frequently (and understandably) emphasize the daunting array of threats to aquatic ecosystems, Thanksgiving seems a good time to reflect on reasons for optimism and, well, gratitude. I live near Cleveland, a city that since the 1960s has been known primarily for sports heartbreaks and the rather incongruous event of a river catching fire.

The Cuyahoga runs through the middle of Cleveland and was the pulsing heart of the city’s industrial might. Beginning in the late 19th century, steel factories and John D. Rockefeller’s oil refineries lined the river, fueling Cleveland’s rise as an industrial powerhouse and (at one time) fifth-largest city in the country. But over that century, the river’s pulsing heart became clogged with sludge. In June 1969, at an extreme bend in the river (Cuyahoga comes from a Native American word meaning “crooked river”), debris soaked in oil and solvents caught fire from a wayward spark.

The resulting fire wasn’t very big—ironically, it wasn’t even big for a Cuyahoga River fire. There had been several before, including one in 1952 which caused approximately $1 million in damages to a shipyard and bridge. And several other industrial rivers in the United States had previously caught fire. But the 1969 Cuyahoga fire occurred just as this country was becoming aware of environmental degradation. Time magazine ran an article featuring the Cuyahoga fire as a symbol of the nation’s pollution problem (the article was illustrated by a photo of the 1952 fire, as the 1969 event was out before any photographers arrived).

The river and lake are dramatically improved — and for that, Clevelanders can be very thankful. And the local and national efforts that were in part inspired by the burning river have made similar progress across the country. Though problems remain, we can all be thankful that our lakes and rivers are much cleaner than they were a generation ago.